Non-Invasive Physiological Measures of Covert Visuospatial Attention: A Methodological Review

Abstract

Covert visuospatial attention refers to the selective enhancement of processing visual locations while suppressing other locations, without shifting our gaze. Because this is a purely internal process, measuring it generally requires careful and precise techniques. To date, non-invasive physiological measures have been developed that form powerful tools for capturing this hidden process. This methodological review describes, evaluates and compares the principal non-invasive physiological approaches used to measure covert visuospatial attention, including M/EEG-based measures (event-related potentials/fields, alpha band modulation, multivariate decoding, steady-state visually evoked potentials/fields and rapid invisible frequency tagging), fMRI-based retinotopic decoding, pupillometry and microsaccade-based measures. Each method is evaluated across a set of dimensions that are relevant to the attention researcher: whether it measures anticipatory or reactive attention, the temporal precision, the spatial precision, the amount of visual interference and selectivity. Clear trade-offs emerge between the qualities of different methodologies. This review paper concludes with a table summarising all method evaluations.